I'd like to know what is(are) the purpose(s) of Rext in the BCR402R LE driver circuit.
The BCR402R is a 20 mA constant current LED driver. The application circuit (see below) shows an external resistor Rext which isn't described in the datasheet. So two questions: 1. What is the purpose or Rext? 2. If I omit Rext, should I leave pin 4 open or connect to +Vs?
BCR402R old datasheet – Newer datasheet
(My thoughts: I expect that pin 4 is normally left unconnected, and Rext either allows to get more than 20 mA current from the driver, or it moves the heat out of the LED driver to an external resistor to get better cooling of the LED driver.)
Best Answer
The updated datasheet explains this better. Try to always use the manufacturer's website copy of the datasheet for the most up to date information.
If not used, Rext is omitted/left open.
Additionally, the Application Note provides further information and typical circuits.